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Biochemistry Flashcards

1
Q

Histone Acetylation

A

Relaxes DNA coiling allowing transcription

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2
Q

DNA methylation

A

template strand cytosine and adenine are methylated in DNA replication allowing mismatch repair enzymes to distinguish between old and new strands

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3
Q

Histone methylation

A

inactivates transcription of DNA

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4
Q

Oratic aciduria

A

inability to convert orotic acid to UM becase of defect in UMP synthase. Autosommal Recessive

Inceased orotic acid in urine, megaloblastic anemia(doesnt improve with B12 or folate), failure to thrive. No hyperammonemia

Suppplement with oral uridine

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5
Q

Ornithine transcarbamoylase deficiency

A

Increased orotic acid wit hyperammonemia

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6
Q

Adenosine Deaminase deficiency

A

Excess ATP and dATP imblances nucleotide pool via feedback inhibition of ribonucleotide reductase preventing DNA synthesis and decreasing lympocyte count ->SCID

Autosommal recessive.

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7
Q

Lesch-Nyhan

A

Defective purine salvage due to HGPRT deficiency. X linked recessive.

Excess uric acid production which predisposes to gout.

Retardation, self-mutilation, aggression, hyperuriceia, gout, choreoatetosis.

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8
Q

Nucleotide excision repair

A

Specific endoucleases release the oligonucleotide containing damaged bases; DNA polymerase and ligase fill and reseal the gap

Repairs bulky helix distorting lesions

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9
Q

Xeroderma pigmentosum

A

prevents repair of pyrimidine dimers because of ultraviolet light exposure

Thiamine-Thiamine

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10
Q

Base excision repair

A

Specific glycosylases recognize and remove damaged bases, apurinic/apyrimidinic endonuclease cuts DNA at both apurinic and apyrimidinic sites, empty sugar is removed, gap is filled and resealed

Important in repair of spontaneous/toxic deamination

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11
Q

Mismatch repair

A

newly synthesized strand is recognized, mismatched nucleotide are removed, gap is filled and resealed

Mutated in HNPCC, BRCA1/2

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12
Q

Nonhomologous end joining

A

Brings together 2 ends of DNA fragments to repair double stranded breaks. No requirement for homology

Mutated in Ataxia telangiectasia

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13
Q

RNA polymerases I, II, III

A

RNA poly I - rRNA
RNA poly II- mRNA
RNA poly III- tRNA

a-Amantin inhibits RNA polymerase II and can cause hepatotoxicity

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14
Q

Smooth ER functions

A

Steroid synthesis and detoxification of drugs and poisons.

Liver hepatocytes and steroid hormone cells of the adrenal cortex are rich in SER

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15
Q

I cell disease

A

Failure of addition of m-6-p to lysosome proteins(enzymes are secreted outside the cell instead of being targeted to the lysosome). Results in coarse facial features, clouded corneas, restricted joint movement, and high plasma levels of lysosomal enzymes. Fatal in childhood

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16
Q

Peroxisome

A

Catabolism of very long fatty acids and amino acids

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17
Q

Chediak Higashi syndrome

A

Mutation in lysosomal trafficking regulator gene(LYST), whose product is required for the microtubule dependent sorting of endosomal proetins into late multivesicular endosomes. Results in recurrent pyogenic infections, partial albinism, and peripheral neuropathy

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18
Q

Kartagener’s

A

Immotile cilia due to dynein arm defect

Infertility, bronchiectasis, recurrent sinusitis, situs inversus.

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19
Q

Vimentin

A

Connective tissue

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20
Q

Desmin

A

Muscle

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21
Q

Cytokeratin

A

epithelial cells

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22
Q

GFAP

A

Neuroglia

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23
Q

Neurofilaments

A

neurons

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24
Q

Ouibain inhibitor

A

Na-K Atpase inhibitor, Binds to K+ site.

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25
Q

Osteogenesis imperfecta

A

Type 1 collagen defect. Problem forming triple helix during disulfide bond formation.

Brittle bone disease. AD

Multiple fractures with minimal trauma
Blue Sclera
Hearing loss
Dental imperfections(lack of dentin)

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26
Q

Ehlers-danlos

A

Type 3 collagen defect, problems with covalent cross linkage with Cu2+ lysyl oxidase

Faulty collagen synthesis causing hyperextensible skin, tendency to bleed, hypermobile joints. AD or AR

Associated with joint dislocation, berry aneurysms, organ rupture.

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27
Q

Alport syndrome

A

Type 4 collage defect

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28
Q

Southern Blot

A

DNA

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29
Q

Northern Blot

A

RNA

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30
Q

Southwestern blot

A

DNA-binding proteins

31
Q

Codominance

A

Both alleles contribute to the phenotype of the heterozygote

32
Q

Variable expressivity

A

Phenotype varies among individuals with same genotype

NF1

33
Q

Incomplete penetrance

A

Not all individuals with a mutant genotype show the mutant phenotype

BRCA1

34
Q

Pleiotropy

A

One gene contributes to multiple phenotypic effects

PKU

35
Q

Imprinting

A

Differences in gene expression depend on whether the mutation is of maternal or paternal origin

Prader willi and Angelmans syndrome

36
Q

Anticipation

A

Increased severity or earlier onset of disease in succeeding generations

Huntingtons

37
Q

Loss of heterozygosity

A

If a patient inherits or develops a mutation in a tumor suppressor gene, the complementary allele must be deleted/mutated before cancer develops. This is not true of oncogenes

RB- two hit hypothesis

38
Q

Dominant negative mutation

A

Exerts a dominant effect. A heterozygote produces a nonfunctional altered protein that also presents the normal gene product from functioning.

39
Q

linkage disequilibrium

A

Tendency for certain alleles at 2 linked loci to occur together more often than expected by chance. Measure in a population, not in a family.

40
Q

Mosaicism

A

Occurs when cells in the bod differ in genetic makeup due to postfertilization loss or change of genetic information during mitosis.

41
Q

Locus heterogeneity

A

Mutations at different loci can produce the same phenotype

Marfans syndrome, albinism

42
Q

Heteroplasmy

A

Presence of both normal and mutated mtDNA resulting in variable expression in mitochondrial inherited disease.

43
Q

Prader WIlli syndrome

A

Paternal allele is not expressed. Chromosome 15

Mental retardation, hyperphagia, obesity, hypogonadism, hypotonia

44
Q

Angelman’s syndrome

A

Maternal allele is not expressed. Chromosome 15

Mental retardation, seizures, ataxia, inappropriate laughter

45
Q

Mitochondrial myopathies

A

Group of rare disorders resulting from mutations affecting mitochondrial function. Often presents with myopathy and CNS disease

Ragged Red muscle fibers

46
Q

Hereditary hemorrhagic telangiectasia (Osler-weber-Rendu syndrome)

A

Disorder of blood vessels.

Telangiectasia, recurrent epistaxis, skin discolorations, Arterioenous malformatons.

47
Q

Neurofibromatosis type 1

A

cafe-au-lait spts, neural tumors, lisch nodules(pigmented iris hamartoas), scolios, optic pathway gliomas

Long arm of chromosome 17

48
Q

Neurofibromatosis type 2

A

Bilateral acoustic schwannomas, juvenile cataracts.

Chromosome 22

49
Q

N-acetylcysteine

A

Cleaves disulfide bonds within mucous glycoproteins

50
Q

Duchenne’s Muscular dystrophy

A

X-linked frameshift mutation. Deletion of dystrophin gene, accelerated muscle breakdown. Weakness begins in pelvic girdle muscles and progresses superiorly. Pseudohypertrophy of calf muscles due to fibrofatty replacement of muscle; cardiac myopathy. Use of Gowers’ maneuver, requiring assitance to stand up.

Onset before 5 years old, increased Creatine kinase due to muscle breakdown

51
Q

Becker’s muscular dystrophy

A

X linked mutated dystrophin gene. Less severe than duchennes. Onset in adolescence or early adulthood.

52
Q

Fragile X syndrome

A

X linked defect affecting the methylation and expression of the FMR1 gene. Trinucleotide repeat of CGG. The 2nd most common cause of genetic mental retardation after down syndrome.

Extra large testes, ears, jaw

53
Q

Trinucleotide repeat disease

A

Fragile X syndrome = CGG
Friedrich’s ataxia = GAA
Huntingtons disease = CAG
Myotonic dystrophy = CTG

54
Q

Down syndrome clinical findings

A

Mental retardation, flat facies, prominent epicanthal folds, simian crease, duodenal atresia, congenital heart disease. Increased ALL and alzheimers disease.

decreased a-FP, estriol. Increased B-hCG and inhibin A

Most common cause of genetic mental retardation.

55
Q

Edwards syndrome

A

Trisomy 18. Severe mental retardation, rocker bottom feet, micrognathia, low set ears, clenched hands, prominent occiput, congenital heart disease. Death after 1 year of birth`

decreased a-FP, estriol, B-hCG. Normal inhibin A

56
Q

Patau’s syndrome

A

sever mental retardation, rocker bottom feet, microphthalmia, microcephaly, cleft lip/palate, holoprosencephaly, polydactyly, congenital heart disease. Death within 1 year of birth

Trisomy 13.

Decreased B-hCG, PAPP-A and increased nuchal translucency.

57
Q

Cri-du-chat syndrome

A

Congenital microdeletion of short arm of chromosome 5.

Microcephaly, moderate to severe mental retardation, high pitched crying/mewing, epicanthal folds, cardiac abnormalities.

58
Q

22q11 deletion syndromes

A 
CATCH-22
Cleft palate
Abnormal facies
Thymic aplasia
Cardiac defects
Hypocalcemia
59
Q

Kwashiorkor

A

Protein malnutrition resulting in skin lesions, edema, liver malfunction. Clinical picture is a small child with a swollen belly

MEAL
Malnutritrion
Edema
Anemia
Liver(fatty)
60
Q

Marasmus

A

Energy malnutrition resulting in tissue and muscle wasting, loss of subcutaneous fat and variable edema.

61
Q

Pyruvate dehydrogenase complex deficiency

A

Causes backup of substrate resulting in lactic acidosis. Most cases are due to mutations in X-linked gene for E1-a subunit of PDC

Neurologic defects starting in infancy

Treat with increased intake of ketogenic nutrients Lysine and Leucine.

62
Q

Superoxide dismutase

A

O2- to H202

63
Q

Myeloperoxidase

A

H202 to HOCL-

64
Q

NADPH oxidase

A

O2 to O2-

65
Q

Essential frutosuria

A

Involves a defect in fructokinase. Autosomal recessive. A benign, asymptomatic condition since fructose is not trapped in cells. Fructose in blood and urine

66
Q

Fructose intolerance

A

Hereditary deficiency of aldolase B. Autosomal recessive. Fructose 1 phosphate accumulates causing a decrease in available phosphate which inhibits glycogenolysis and gluconeogenesis.

Hypoglycemia, jaundice, cirrhosis, vomiting.

67
Q

Galactokinase deficiency

A

Hereditary deficiency of galactokinase. Galactitol accumulates if galactose is present in diet. Relatively mild condition. Autosomal recessive.

Galactose in blood and urine, infantile cataracts

68
Q

Classic galactosemia

A

Absence of galactose-1-phosphate uridyltransferase. Autosomal recessive. Damage is caused by accumulation of toxic substance(galactitol) in the lens of they eye.

Failure to thrive, jaundice, hepatomegaly, infantile cataracts, mental retardation.

Remove galactose and lactose from diet.

69
Q

Essential amino acids

A

PVT TIM HaLL
Phenyalanine
valine
threonine

Tryptophan
isoleucine
methionine

Histidine
a
Leucine
Lysine

70
Q

Carnitine deficiency

A

inability to transport LCFAS into the mitochondria, resulting in toxic accumulation causing weakness, hypotonia, and hypoketotic hypoglycemia

71
Q

Type 1 hyper-chylomicronemia

A

Increased levels of chylomicrons, TG, cholesterol

AR. Lipoprotein lipase deficiency or altered apolipoprotein C-II. Causes pancreatitis, hepatosplenoegaly, and eruptive/pruritic xanthomas

72
Q

Type IIa familial hypercholesterolemia

A

Increased LDL, Choleseterol

AD. Absent or decreased LDL receptors causing accelerated atherosclerosis, tendon xanthomas and corneal arcus

73
Q

Type IV hypertriglyceridemia

A

Increased VLDL and TG

AD. Hepatic overproduction of VLDL. Causes pancreatitis.

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